This patch adds support for fake hosting services that Review Board

does not provide, but Power Pack does. These services do not implement

anything, but are instead shown in the "Add Repository" form when Power

Pack is not enabled.
When a fake hosting service is selected in the form, an advertisement

for Power Pack is shown and the form becomes unsubmittable. This is to

ensure that users don't end up getting an error when trying to use the

hosting service that is not actually registered in the database.
A large portion of this change is updating repositoryform.js to bring

it in line with the rest of our JavaScript by prefixing all jQuery

objects with $.

Ran unit tests.
Manually verified that the fake hosting service appeared only when

Power Pack was not enabled.